Despite progress made in the treatment and management of asthma, strategies for its prevention remain elusive. Likewise, lead poisoning remains a serious environmental health hazard for U.S. children. The two conditions have similar epidemiologic patterns. Both are prevalent among young children, elements in the physical environment heighten risk of disease, and residing in an urban environment increases the probability of exposure to relevant physical and socioeconomic risk factors. Recent published analyses have suggested a possible relationship between the two disorders. The objective of this study is to use automated data to examine relationships between blood lead levels (BLL) and development of asthma. The study population will be children greater than 2 years of age who have been continuously enrolled in the Henry Ford Health System (HFHS) managed care organization and for whom there is a BLL in the HFHS laboratory results database for 1995-1996. Asthma status will be determined using patient encounter and prescription claims databases. This information will be used to investigate the association of BLL and asthma prevalence at baseline, and to assess BLL as a predictor of development of asthma during a defined follow-up period. Results of this analysis will guide the design of future studies involving primary data collection. Benefits of this study include the ability to use available automated datasets to examine the association of BLL and occurrence of asthma in an ethnically and socioeconomically diverse population, adjusting for demographic variables and adjunct measures of socioeconomic status. Examination of the potential relationship between BLL and asthma is critical, as environmental lead would be a modifiable risk factor for asthma. In addition, information on this relationship can be instrumental in helping to uncover reasons for racial differences in asthma prevalence and gaining more information on ways to prevent or reduce the risk of asthma, especially among urban, minority children.